Cancer of the cervix uteri is the second most common cancer among women worldwide, with an estimated 493,000 new cases and 274,000 deaths in 2002. The field of cervical cancer prevention is rapidly evolving as a consequence of the identification of the cause of the disease: a limited number of viral types from the family of the Human Papillomaviruses (HPV). Indeed, HPV has been recognized as a cause of cervical cancer, and 2 of the oncogenic types, 16 and 18, are together responsible for 70% of the world's cervical cancer cases.
Recently the use of 2 prophylactic vaccines was licensed. Nevertheless, it is likely to be decades before the impact of HPV vaccination on the incidence of cervical cancer can be evaluated. Optimally, these vaccines should be administered before sexual debut and HPV infection. As such, they are of no benefit for women with already existing HPV infection. Treatment (surgery) for HPV infection is often unsatisfactory because of persistence of virus after treatment and recurrence of clinically apparent disease is common. The treatment may require frequent visits to clinics and is not directed at elimination of the virus but at clearing warts. Moreover, it is expected that less prevalent, oncogenic HPV genotypes will take over—at least in part—the place from the currently targeted HPV16 and 18 genotypes. Women with pre-carcinogenic lesions resulting from the widespread HPV infections today represent a highly unmet need.
Thus, a need exists for an efficacious vaccine to prevent and/or treat persistent HPV infection and to prevent cancer that is associated with HPV infection. Effective HPV vaccines would be a significant advance in the control of sexually transmissible infections and could also protect against clinical disease, particularly cancers such as cervical cancer. (see, e.g., Rowen, P. and Lacey, C., Dermatologic Clinics 16 (4): 835-838, 1998).
In the majority of individuals, HPV infections presumably induce strong, local, cell-mediated immunity that results in clearance of the virus and protection against subsequent infection. Virus-specific, human leukocyte antigen (HLA) class I-restricted cytotoxic T lymphocytes (CTL) and HLA class II-restricted helper T lymphocytes (HTL) are known to play a major role in the prevention of chronic infection and in viral clearance in vivo (Houssaint et al., 2001; Gruters et al., 2002; Tsai et al., 1997; Murray et al., 1992; Tigges et al., 1992; Bowen and Walker, 2005).
A therapeutic vaccine candidate targeting HPV should elicit strong and multi-specific cellular immune responses. The induction of a strong HPV-specific cellular response—comprising activity of cytotoxic T-cells (CTL) and helper T-cells (HTL)—may be achieved using an epitope-based vaccine approach.
The polyepitope approach to vaccine development is to rationally create a multi-specific cellular response, causing the immune system to be specifically stimulated against multiple selected epitopes that meet stringent criteria. These include CTL epitopes that are presented by MHC-I and are recognized by cytotoxic T-cells, and HTL epitopes that bind MHC II and are recognized by helper T-cells. The epitopes are selected in view of their capacity to elicit responses in humans, thereby aiming for a large population coverage (by targeting major HLA class-I alleles as well as major HLA class-II alleles).
The technology relevant to polyepitope vaccines is developing and a number of different approaches are available which allow simultaneous delivery of multiple epitopes. Several independent studies have established that induction of simultaneous immune responses against multiple and individual peptides can be achieved (Doolan et al (1997), Bertoni and colleagues (1997)). In terms of immunization with polyepitope nucleic acid vaccines, several examples have been reported where multiple T cell responses were induced (Thomson et al., 1995; Woodberry et al., 1999; Mateo et al., 1999; Ishioka et al., 1999; WO04/031210, Innogenetics N. V. et al.).
The efforts to develop an effective treatment for HPV-related disease are narrowly focused. Most studies are concentrating on the HPV type 16 E6 and/or E7 protein. Also WO05/089164 (Pharmexa et al.) discloses HPV polyepitope constructs focussing on E6 and E7, and additionally E1 and E2 proteins. During the papillomavirus life cycle, the HPV proteins (E1, E2, E4, E5, E6, E7, L1 and L2) are differentially expressed. Moreover, during progression from CIN1 to CIN3, the extent of expression of the different HPV proteins is changing (Doorbar, 2005). Targeting all 6 early proteins (E1, E2, E4, E5, E6 and E7) thus provides a way to induce efficient immune responses directed to all stages of the virus life cycle, irrespective of the CIN grade.
Although E4 and E5 were screened for immunogenic epitopes, WO05/089164 was unsuccessful in obtaining reactive peptides. It is indeed known that most of the HPV proteins are comparatively small and might therefore not comprise many reactive epitopes.
The present inventors however have now determined several immunogenic epitopes in the E4 and E5 proteins of the high risk HPV genotypes HPV16, 18, 31 and 45. Moreover, the present inventors were successful in creating a potent, multi-specific and full-spectrum vaccine addressing the different stages of HPV infection, and thereby broadening the treatment window. Where others, focusing on E6 and/or E7 are mainly targeting CIN2 and CIN3, this vaccine allows to treat earlier stages of disease as well as persistent infection, thereby further reducing the chance of developing cervical cancer.
The polyepitope constructs are designed to induce an immune response to at least 4 distinct CTL and 1-3 HTL epitopes per HPV genotype in the majority of subjects infected with one of the four most prevalent, high risk HPV genotypes (HPV16, 18, 31 and 45) irrespective of their ethnic origin.